1. Field of the Invention
The present invention relates to an electric motor driving apparatus, having a failure detection circuit, which drives a three-phase-winding electric motor or a multiplex-winding electric motor.
2. Description of the Background Art
In electric motor control, if a current sensor for detecting DC current on a DC power supply side or output phase current has failed, an electric motor cannot be controlled. Therefore, an electric motor driving apparatus needs to determine whether or not the current sensor has failed.
As a method for detecting failure of the current sensor, a method is disclosed in which DC current is detected by a current sensor connected to a DC power supply side, output phase current is calculated based on the detection, and failure of the current sensor is detected in a zero voltage vector period (for example, Patent Document 1).
Patent Document 1: Japanese Laid-Open Patent Publication No. 2010-136581 (paragraphs [0022] and [0026], and FIG. 1)
In the invention disclosed in Patent Document 1, since failure of the current sensor is determined only when the rotation rate of the electric motor is zero, there is a problem that failure of the current sensor cannot be detected when the rotation rate of the electric motor is other than zero, that is, during normal operation.